Electrode element for an energy storage unit, energy storage unit, and method for producing electrode element

ABSTRACT

An electrode element ( 1 ) for an energy storage unit ( 200 ), such as a capacitor, has an electrode body ( 100 ) made of an active electrode material (E), wherein the electrode body ( 100 ) includes one or more of: at least one cavity ( 110 ) on its surface or in its interior; at least one partial volume ( 120 ) of lower density; and/or a surface coating (D) covering at least a portion of the surface of the electrode body ( 100 ), such that the surface area covered by the surface coating (D) remains unwetted when in contact with an electrolyte. Energy storage units ( 200 ) incorporating the electrode element ( 1 ) are particularly suitable for use in implantable electrotherapeutic devices.

FIELD OF THE INVENTION

The invention relates to an electrode element for an energy storageunit, in particular for use in an implantable electrotherapeutic device;to a method for producing an electrode element; to an energy storageunit, in particular for use in an implantable electrotherapeutic device;and to an implantable electrotherapeutic device, in particular animpulse generator such as, for example, a cardiac pacemaker, animplantable cardioverter-defibrillator, or a neurostimulator.

BACKGROUND OF THE INVENTION

Suitable energy storage units for implantable electrotherapeutic devicesinclude batteries, e.g., lithium batteries and lithium ion batteries,and/or capacitors, e.g. electrolytic capacitors. Such energy storageunits include electrodes having an electrode body made of an activeelectrode material.

For example, document DE 10 2011 089 174 A1 describes a battery anodecomponent having least two spatially separated recesses serving aslithium receiving chambers. The recesses are separated from one anotherby a current collector component having a predetermined breaking point,whereby only very little lithium is released if the current collectorcomponent ruptures.

However, in prior energy storage unit production methods, fluctuationsin the quality of the raw electrode materials used, and processfluctuations during production of the electrodes, can causesignification variation in the activity of the manufactured electrodes,and thus in the storage capacity of the energy storage units in whichthe electrodes are installed.

In order to provide the required energy storage capacity within aprespecified tolerance, the raw electrode materials are selected, and ifnecessary the configuration of the active electrode material of theelectrode bodies may be varied. This has the disadvantage that theelectrode design is generally made experimentally, and the testedelectrodes may be unusable in end products, leading to higher productioncosts. If electrode configuration is altered to attain a desired energydensity, the electrode's external dimensions may vary enough thatcomponent fit during assembly of the energy storage unit is no longeraccurate. Likewise, in order to attain a prespecified energy densitywith a modified configuration, the manufacturing and assembly tools andprocesses may require modification. The production and modification ofsuch tools is very expensive, particularly as modification may requireoverall tool redesign.

SUMMARY OF THE INVENTION

The invention provides an electrode element for an energy storage unit;a method for producing an electrode element; an energy storage unit; andan implantable electrotherapeutic device using the energy storage unit,all of which are improved with respect to the aforementioned drawbacks.In particular, the invention seeks to provide an energy storage unithaving lesser production-related fluctuations in its storage capacity,and which can be produced in a cost-effective manner.

A first aspect of the invention relates to an electrode element for anenergy storage unit, particularly a capacitor, wherein the electrodeelement has an electrode body that is formed from active electrodematerial, and wherein:

(1) the electrode body includes at least one cavity on its surface or inits interior, wherein the mass of the electrode body is adjusted, inparticular to a desired value, by the cavity; and/or(2) the electrode body includes at least one partial volume of lowerdensity, wherein the active electrode material has a lower densitywithin the partial volume than outside of the partial volume, wherebythe mass of the electrode body is adjusted, in particular to a desiredvalue, by the partial volume of lower density; and/or(3) the electrode body includes a surface coating, e.g. an impregnatingagent such as silicone (adhesive), epoxy resin, polymers, or varnish,wherein the surface coating covers at least a portion of the surface ofthe electrode body, and wherein the surface coating is designed suchthat the surface of the electrode body covered by the surface coatingremains unwetted when in contact with an electrolyte.

The electrode element preferably includes a terminal lead electricallyconnected to the electrode body.

The mass (and thus the electrode activity) of the active electrodematerial is reduced by the cavity or cavities, and/or by the partialvolume(s), compared to an electrode element lacking the cavity/cavitiesand/or partial volume(s). Likewise, the accessible active surface of theelectrode body may be reduced in a controlled manner using the surfacecoating.

By these arrangements, when the electrode element is used in an energystorage unit, the storage capacity of the energy storage unit mayadvantageously be simply and accurately adjusted, since this storagecapacity is a function of the mass of the electrode body and/or of itssurface area that can be wetted by an electrolyte. This makes itpossible to compensate for fluctuations in the properties of the rawelectrode materials used, and/or for fluctuations in manufacturingparameters. Thus, complex tests required in prior production methods,and expensive tool redesign or replacement, are unnecessary, and energystorage units with low storage capacity tolerances can be produced withless expense.

Throughout this document, “electrode element” refers to a componentsuitable for use as an electrode, in particular an anode, in an energystorage unit such as a capacitor, in particular an electrolyticcapacitor. The electrode includes a unitary electrode body having anydesired shape and is made of an active electrode material, but may haveadditional components (e.g. a surface coating and/or filler material) inaddition to the electrode body.

“Active electrode material” refers to a material that is configured torelease or receive charge carriers (e.g., electrons or ions) in anenergy storage unit such as a capacitor. The active electrode materialpreferably includes or essentially consists of a valve metal, inparticular aluminum, tantalum, niobium, or zirconium. The term “valvemetal” refers to a metal that, through anodic oxidation, forms a coatingof metal oxide that is electrically non-conducting. Such valve metalsmay be used for electrodes, e.g., anodes of electrolytic capacitors,wherein the metal oxide coating functions as dielectric material.

Depending on the material properties of the active electrode material,the mass of the active electrode material, and the shape of theelectrode body, the electrode element has a certain activity, i.e., aspecific tendency to receive or release charge carriers. The higher thisactivity, the greater the storage capacity of an energy storage unit inwhich the electrode element is used as electrode, in particular as ananode.

In versions of the electrode element having the aforementioned cavity,the cavity may be defined by a depression or blind hole in the electrodebody, by through-hole extending through the electrode body, or by ahollow chamber within the interior of the electrode body. The cavity mayhave any shape, e.g. it may have a polygonal, round, or oval-shapedcross-section. Cavities of different shapes and sizes may also becombined with one another, e.g., an electrode body may include some orall of blind holes, through-holes, and interior chambers. The cavity orcavities may be added to the electrode body in a controlled mannerduring the electrode body's production process. Adding cavities allowsthe activity of the electrode element to be adjusted in a particularlysimple and variable manner.

In versions of the electrode element having the aforementioned partialvolumes of lower density, partial volumes may likewise be disposed onthe surface of, or within the interior of, the electrode body. The lowerdensity of the partial volume may be attained, for example, using activeelectrode material having higher porosity within this partial volume.For example, the electrode body may be shaped by pressing powdered rawelectrode material, wherein the partial volume(s) are appropriatelyformed by application of lesser pressure, resulting in correspondinglyhigher porosity. Porosity variation can depend on the properties of theraw electrode material, for example, the grain size of the powder thatis used as raw material.

In versions of the electrode element having the aforementioned surfacecoating, the electrode body may have capillaries or other cavities sothat one or more portions of the electrode body have a porous structure,with the surface coating being configured such that the surface coatingis drawn into the capillaries of the electrode body after application tothe electrode body. In particular, the viscosity of the surface coatingmay be chosen such that the coating is drawn into the capillaries of theelectrode body after being applied to the electrode body. The surfacecoating remains in or on the electrode body when hardened, such that itimmovably remains in place.

The surface coating prevents an electrolyte, in particular a liquidelectrolyte, from wetting the region of the electrolyte body covered bythe surface coating. Thus, the coated region of the active electrodematerial is functionally deactivated. The dosing (amount/thickness) ofthe surface coating determines the extent of deactivation, and thus theeffect on the activity of the active electrode material. Adjusting thedosing of the surface coating to advantageously allows adjustment of thedeactivation (and conversely the activity) of the electrode element.

In some versions of the invention, the cavity or the partial volume oflower density form a separation boundary designed such that theelectrode body may be broken, cut, or otherwise mechanically separatedat the separation boundary into separate body segments. The separationboundary is designed as a predetermined mechanical separation boundary,wherein the electrode body may be mechanically separated at the targetbreaking point by breaking, cutting, or otherwise separating theelectrode body into a first body segment and a second body segment. Themechanical separation effects the controlled reduction in the mass ofthe active electrode material. Following separation, the first bodysegment and/or the second body segment may be used as separate electrodeelements, e.g., in an energy storage unit. This has the advantage that,even after the conclusion of the essential production steps for theelectrode element, its activity may be adjusted in a simple and easilycontrolled manner, e.g., during assembly of an energy storage unit. Theseparation boundary may be formed by a cavity, e.g. a notch or channelin the surface of the electrode body, or by a region of lower density inthe active electrode material, or by a hollow chamber filled with afiller material having a lower density than the active electrodeelement. The separation boundary may be defined by multiple suchcavities, regions, or chambers, as by arranging them along a path alongwhich the electrode element is to be broken or otherwise separated.

In another version, the electrode body includes a first partial body, asecond partial body, and a connecting element, all made of the activeelectrode material, wherein the first partial body and the secondpartial body are mechanically connected to one another by the connectingelement. The connecting element extends along a longitudinal axisbetween first partial body and the second partial body, and has asmaller cross-sectional area perpendicular to the longitudinal axis thanthe first partial body and the second partial body, thereby forming acavity between the partial bodies and the connecting element. The firstpartial body and the second partial body may be mechanically separatedby severing the connecting element, whereby the connecting elementserves as a separation boundary. Severing the connecting element effectscontrolled reduction in the mass of the active electrode material. Thus,once essential production steps are completed, the activity of theelectrode element may be simply reduced, e.g., during the assembly of anenergy storage unit. The partial bodies and the connecting elementinclude or essentially consist of the same active electrode material,e.g., a valve metal. The electrode element is particularly suited foruse as an electrode in an electrolytic capacitor. The connectingelements may be wires or other linking structures made of the activeelectrode material.

The electrode body may include multiple partial bodies and connectingelements, wherein each pair of partial bodies is mechanically connectedby a connecting element, and wherein the connecting elements havesmaller cross-sectional areas than their adjacent partial bodies,whereby cavities are formed between the partial bodies adjacent theirconnecting elements. The partial bodies may be mechanically separated bysevering the connecting elements therebetween. In such electrode bodies,the partial bodies may be connected in a linear chain-like manner by theconnecting elements, or branches may be provided so that a two orthree-dimensional arrangement of partial bodies results.

In another version, the electrode element includes a filler material,such as ceramic or glass, within the cavity or cavities of the electrodebody. The filler material may be in the interior of the electrode body,and may be particles having spherical or other shapes with diameters of0.1 μm to 3 mm, preferably 0.1-50 μm or 100-1000 μm. More generally, theparticles may have a mean diameter or mean grain size in the order ofmagnitude of the powder size of the raw material of the active electrodematerial. Typically, a raw material powder having a mean grain size ofless than 0.6 mm is used, preferably in the range of 75 μm to 150 μm.The term “mean diameter” or “mean grain size” refers to the arithmeticmean of all diameters of the particles, or to the median of the sizedistribution of all particles.

Another aspect of the invention relates to a method for manufacturing anelectrode element for an energy storage unit, wherein an electrode bodyis formed of an active electrode material, in particular in a shapingstep, and wherein:

(1) the mass of the active electrode material of the electrode body isreduced, and/or(2) a surface coating is applied to cover at least a portion of thesurface area of the electrode body, so that the surface area of theelectrode body covered by the surface coating remains unwetted when incontact with an electrolyte.

“Shaping step” refers to any production step wherein the electrode bodyreceives its shape. A shaping step may be, for example, a metal castingmethod, a sintering method, a punch method, or a cutting method. Themanufacturing method may further include the step of electricallyconnecting the active electrode material to a terminal lead.

When the manufacturing method includes the step of reducing the mass ofthe electrode body (as by adding a cavity to the electrode body, and/orby providing a partial volume having reduced density), the activity ofthe electrode element may advantageously be adjusted such that an energystorage unit using the electrode element as an electrode has a desiredstorage capacity. The activity of the electrode element may be adjustedduring production, as by machining out a defined volume in order toadjust the mass of the electrode body, and/or by providing one or morecavities to define a separation boundary such that the activity of theelectrode element may be adjusted by separating the electrode body atthe separation boundary.

When the manufacturing method includes the step of providing a surfacecoating on the surface of the electrode body, the surface coatingprevents electrolyte from wetting the region of the electrode materialcovered by the surface coating, functionally deactivating the activeelectrode material at this region. The dosing of the surface coatingdetermines the extent of deactivation. To perform this step, aninitially liquid impregnating agent or other surface coating is appliedto at least a portion of the electrode body, which preferably hascapillaries or other pores etched or otherwise formed therein, orotherwise has a permeable structure. When the surface coating is appliedto the electrode body, the surface coating is drawn into the pores. Thesurface coating preferably has a viscosity and/or other properties suchthat it is drawn into the pores of the electrode body after beingapplied thereon. If the electrode body is made of a valve metal, thesurface coating is applied after the formation of the nonconductingmetal oxide coating of the valve metal. The surface coating hardensafter it enters the pores, such that it thereafter remains in place onand within the electrode body.

In the shaping step, the electrode body may be shaped by pressing andsintering powdered raw material (with or without binding agent).Alternatively or additionally, the electrode body may be shaped bypunching and/or cutting (e.g., by means of laser, water jet, electronbeam, or sawing).

When the manufacturing method includes the step of reducing the mass ofthe electrode body by forming a cavity upon or within the electrodebody, formation of the cavity reduces the mass of the active electrodematerial. The cavity may be formed after formation of the electrodebody, e.g., after the conclusion of the shaping step, by removing activeelectrode material from the electrode body. The active electrodematerial may be removed by drilling, milling, punching, or othermethods. The formed cavity may be, for example, a blind hole or athrough-hole.

The active electrode material may also or alternatively be removed byproducing a notch or other cavity in the outer surface of the electrodebody, or by separating a portion of the electrode body, as by sawing,grinding, or breaking.

Where the active electrode material is a valve metal, the cavity ispreferably formed following formation of a metal oxide coating, whichmay occur by means of anodic oxidation of the valve metal. Preferably,following formation of the cavity, a metal oxide coating of the valvemetal is formed within the cavity by anodic oxidation.

The cavity may be formed during the shaping step by displacing activeelectrode material during the formation of the electrode body. This canbe done by pressing in cavities (e.g., blind holes or other depressions,or through-holes, preferably having rounded surfaces). The cavities arepreferably formed such that the nominal outer dimensions of theelectrode body are retained. Pressing is preferably performed by meansof a stamp, most preferably an adjustable stamp.

The electrode body is also preferably performed by pressing, wherein thepressing of the cavities is preferably accomplished simultaneously withthe pressing of the electrode body.

In an exemplary manufacturing method, at least one partial volume of theelectrode body is formed during the formation of the electrode body(e.g, during the shaping step), wherein the active electrode materialhas a lower density within the partial volume than outside of thepartial volume.

In an alternative exemplary manufacturing method, one or more cavitiesformed in the electrode body, and/or one or more partial volumes oflower density, define a separation boundary within the electrode body,allowing mechanical separation of the electrode body at the separationboundary into a first body segment and a second body segment. The activeelectrode material is preferably a valve metal, wherein mechanicalseparation of the electrode body at the separation boundary into two ormore body segments is done after formation of a metal oxide coating ofthe valve metal. After such separation, a metal oxide coating is againpreferably formed on the body segments where separation occurred.

In another version of the manufacturing method, the electrode elementincludes two or more partial bodies, each being connected to at leastone other partial body, or to the remainder of the electrode body, by aconnecting element. The partial bodies and the connecting element areeach made of the active electrode material. Each connecting elementextends along a longitudinal axis, and has a smaller cross-sectionalarea perpendicular to the longitudinal axis than the first partial bodyand the second partial body, thereby defining a cavity at the connectingelement between the portions of the electrode body joined by theconnecting element. The connecting element defines a separation boundarywhereby the electrode body may be mechanically separated by severing theconnecting element, either during or after production of the electrodebody. The connecting element may be defined by a wire or other link madeof the active electrode material. The active electrode material ispreferably a valve metal, wherein the connecting element is severedfollowing formation of a metal oxide coating of the valve metal of theelectrode body. Preferably, following such severing, a metal oxidecoating of the valve metal is formed at the severed location.

In versions of the manufacturing method wherein cavities are provided onor within the electrode body, the cavity or cavities may be filled witha filler material, for example, ceramic or glass. The filler materialmay stabilize the mechanical structure of the electrode body. If theelectrode element is used as an electrode in an electrolytic or othercapacitor, the filler material is preferably chosen such that it doesnot negatively impact the functioning of the capacitor. The fillermaterial is preferably added to the electrode body during or after theshaping step in which the electrode body is formed, and may beaccomplished by pressing the filler material into the electrode body.The filler material may be particles having spherical shapes withdiameters of 0.1 μm to 3 mm, preferably 0.1-50 μm or 100-1000 μm. Moregenerally, the particles may have a mean diameter or mean grain size inthe order of magnitude of the powder size of the raw material of theactive electrode material. Typically, a raw material powder having amean grain size of less than 0.6 mm is used, preferably in the range of75 μm to 150 μm.

During manufacture, the activity of the electrode element may bemeasured, and thereafter the cavity and/or the partial volume of lowerdensity may be formed, and/or the surface coating may be applied, suchthat the activity of the electrode element is adjusted to a targetvalue. The adjustment may be controlled by remeasuring the activityafter formation of the cavity and/or the partial volume of lowerdensity, and/or after the application of the surface coating. Thecontrol measurement may be performed on a random sample of the producedelectrode elements, that is, the calibration may be based on randomsamples and applied by lot. The activity of the electrode element may bemeasured by determining a storage capacity of an energy storage unitwherein the electrode element forms an electrode. Alternatively,activity measurement may be done indirectly, e.g., by determining themass of the active electrode material.

Another aspect of the invention relates to an energy storage unit, inparticular for use in an implantable electrotherapeutic device, whereinthe energy storage unit has at least one electrode element as describedabove, and wherein the electrode element forms an electrode, inparticular an anode, of the energy storage unit. The energy storage unitmay be defined by a capacitor, in particular an electrolytic capacitor.

Another aspect of the invention relates to a method for manufacturing anenergy storage unit wherein the energy storage unit includes anelectrode element as described above, wherein the electrode elementforms an electrode, preferably an anode, of the energy storage unit, andwherein a storage capacity of the energy storage unit is adjusted orcalibrated by reducing the mass of the active electrode material of theelectrode body, and/or or by applying the surface coating to theelectrode body of the electrode element. Adjustment of the storagecapacity of the energy storage unit preferably occurs by less than 20%,in particular by less than 5%.

Another aspect of the invention relates to an implantableelectrotherapeutic device, in particular an impulse generator, whereinthe implantable electrotherapeutic device includes at least one energystorage unit as described above. The energy storage unit acts as anenergy source for operating the implantable electrotherapeutic device.The impulse generator may be a cardiac pacemaker, an implantablecardioverter-defibrillator (ICD), or a neurostimulator.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the accompanying drawings:

FIG. 1 depicts an exemplary electrode element having cavities in theelectrode body;

FIGS. 2a-2c illustrate an exemplary version of the electrode elementhaving a cavity, and schematically depict a method for adjustingelectrode activity;

FIGS. 3a-3c illustrate another exemplary version of the electrodeelement having a separation boundary, and schematically depict anothermethod for adjusting electrode activity;

FIG. 4 illustrates another version of the electrode element, havingpartial bodies and connecting elements;

FIG. 5 illustrates another exemplary version of the electrode elementhaving cavities formed therein;

FIG. 6 illustrates another version of the electrode element having afiller material in the interior of the electrode body;

FIG. 7 illustrates another version of the electrode element having apartial volume of different density;

FIG. 8 illustrates another version of the electrode element having asurface coating;

FIG. 9 illustrates an exemplary version of an energy storage unit.

DETAILED DESCRIPTION OF EXEMPLARY VERSIONS OF THE INVENTION

Expanding on the foregoing discussion, FIG. 1 is a sectionalillustration of an exemplary electrode element 1 having a unitaryelectrode body 100 made of an active electrode material E. In theexemplary version depicted, the electrode body 100 has two cavities 110or cavities, wherein one of the cavities 110 is designed as a blindhole, that is, a cavity that does not go all the way through the body100, and the other cavity 110 is embodied as a through-hole, that is, asa cavity that goes entirely through the body 100.

The cavity 110 allows the activity of the electrode element 1 to beadjusted to a desired value as early as during manufacture of theelectrode body 100, by reducing the mass of the electrode body 100. The“activity” of the electrode element 1 means the tendency to receive orrelease charge carriers, this tendency leading to a specific storagecapacity of an energy storage unit (such as a capacitor) if theelectrode element 1 is used as an electrode, in particular as an anode.This activity is in particular a function of the mass of the electrodebody 100, or of the surface area of the electrode body 100 accessible toan electrolyte.

FIGS. 2a-2c depict another exemplary implementation of the electrodeelement 1, wherein the electrode element 1 includes an electrode body100 and a conductively connected connecting pin 140 to which electricalconnections can be made. FIG. 2a depicts a top view of the electrodeelement 1. The electrode body 100, which is made of the active electrodematerial E, has an essentially semi-circular shape, wherein a roughlysemi-circular cavity 110 has been formed in the straight side of thesemi-circle. FIG. 2b is a sectional view of an electrode element 1shaped as in FIG. 2 a.

FIG. 2c provides a schematic depiction of a manufacturing method for theelectrode element 1. In this method, first the semi-circular electrodebody 100 is made from the active electrode material E and connected tothe connecting pin 140. Thereafter, an electrode piece 150 is separatedfrom the electrode body 100, for example by cutting, sawing, or milling.In this way, the mass of the active electrode material E is reduced in acontrolled manner in order to obtain an appropriate desired electrodeactivity when the electrode element 1 is used in an energy storage unit.In this version of the manufacturing method, no cavity 110 is made inthe electrode body 100.

FIG. 3 depicts another exemplary version of the electrode element 1 in atop view (FIGS. 3a and 3b ) and in section (FIG. 3c ). FIG. 3a depictsthe electrode element 1 prior to a separating process, and FIG. 3bdepicts the electrode element 1 following the separating process. Theelectrode element 1 has an essentially semicircular shape and includes aunitary electrode body 100 made of an active electrode material E, and aconnecting pin 140. The electrode body 100 furthermore has cavities 110arranged along a linear path, and which may be formed as through-holesor as blind holes. Together the cavities 110 form a separation boundaryor predetermined breaking point 130 that makes it possible to break orotherwise mechanically separate the electrode body 100 at the separationboundary 130 into a first body segment 131 and a second body segment132. FIG. 3b depicts the first body segment 131 and the second bodysegment 132 following separation at the separation boundary 130.

FIG. 3c depicts an exemplary electrode element 1 in section, wherein theseparation boundaries or predetermined breaking points 130 are definedby cavities 110 in the form of notches. After completion of theessential production steps for the electrode element 1, the mass of theelectrode body 100 may be reduced by separating at the separationboundary 130 in order to adjust the activity of the electrode element 1to a desired value, e.g., in order to calibrate the storage capacity ofan energy storage unit in which the electrode element 1 is used as anelectrode (in particular an anode). One of the body segments 131 and 132may then further be used as an electrode element 1 having reduced massand activity, here preferably the first body segment 131, which bearsthe connecting pin 140.

FIG. 4 depicts a sectional view of an exemplary version of the electrodeelement 1, which in this case has already been produced with bodysegments 400, 401, 402, 403 made of the active electrode material E. Thebody segments 400, 401, 402, 403 are connected to one another viaconnecting elements 410 made of the same active electrode material E(for example, a valve metal) as the body segments 400, 401, 402, 403.The body segments 400, 401, 402, 403 are connected to one another as alinear chain via the connecting elements 410, with the connectingelements 410 extending along a common longitudinal axis L. However, itis also possible to create branched structures or a two orthree-dimensional arrangement of body segments of the electrode body100.

The body segments 400, 401, 402, 403 may be broken, cut, or otherwisemechanically separated from one another at the connecting elements 410.This advantageously allows reduction of the mass of the electrode body100 in a controlled and simple manner even after the essentialproduction steps for the electrode element are finished, and therebyallows adjustment of the electrode activity of the electrode element 1,e.g., when used in an energy storage unit, wherein the electrodeactivity influences the energy storage unit's storage capacity.

The connecting elements 410 may be formed as wires or other linkingstructures bridging the body segments 400, 401, 402, 403. The connectingelements 410 have a smaller cross-sectional area perpendicular to thelongitudinal axis L than the body segments 400, 401, 402, 403, whereby acavity 110 is created between body segments 400, 401, 402, 403 at eachconnecting element 410. The connecting elements 410 thereby defineseparation boundaries between body segments 400, 401, 402, 403.

FIG. 5 depicts a section through an electrode body 100 of an exemplaryelectrode element 1 having cavities 110 defined therein. One of thesecavities 110 is defined as a through-hole, while the other two cavities110 are designed as depressions (blind holes) in the surface of theelectrode body 100. Such cavities 110 may be formed during a shapingstep in the production of the electrode body 100, e.g., by pressing intothe electrode body 100 by means of a stamp.

By selecting the dimensions of the cavities, the mass of the activeelectrode material E is adjusted to a desired value in order to attain adesired activity regardless of variation in the raw electrode materialsand previous production steps. This activity then assists in providingthe desired storage capacity of an energy storage unit incorporating theelectrode element 1.

FIG. 6 is a sectional depiction of an exemplary electrode element 1having cavities 110 within the interior of the electrode body 100. Thesecavities 110 are filled with a filler material F, as depicted atreference numeral 500. This filler material F differs from the activeelectrode material E, and in particular does not have any activeelectrode properties. The filler 500 may be pressed into the electrodebody 100, for example, during a shaping step for the electrode body 100.The volume of the filler 500 may be shaped, sized, and positioned asappropriate for the materials and configuration of a given electrodebody 100. The filler 500 may have a particulate, liquid, or other formwhich accommodates the shape of the cavities 110 when poured or injectedtherein.

The filler material F of the filler 500 allows the mass of the activeelectrode material E, and thus the activity of the electrode element 1,to advantageously be adjusted to a desired value, since the activeelectrode material E of the cavities is replaced by the filler materialF. At the same time, the mechanical stability of the electrode body 100is increased due to use of the filler material F in the cavities 110 inplace of empty voids.

FIG. 7 is a sectional depiction of another exemplary electrode element 1wherein the surface of the electrode body 100 has a partial volume 120therein of lower density. The electrode body 100 has the same activeelectrode material E both within and outside the partial volume 120, butthe density of the active electrode material E within the partial volume120 is lower than outside the partial volume 120.

The activity of the electrode element 1 is therefore reduced compared toan electrode element 1 having uniformly higher density, so that when theelectrode element 1 is used as an electrode (especially as an anode) inan energy storage element, selection of the size and density of thepartial volume 120 determines the element's storage capacity.

The partial volume 120 need not be disposed on the surface of theelectrode body 100, but instead may be situated within the interior ofthe electrode body 100. Rather than being of lower density, one or morepartial volumes may instead be of higher density to allow adaptation ofthe activity of the electrode element 1.

FIG. 8 depicts another exemplary electrode element 1 having an electrodebody 100 made of the active electrode material E, and having a coverlayer made of a surface coating D, for example an impregnating agent, onthe surface of the electrode body 100. The surface coating D preventswetting of the surface of the electrode body 100 with an electrolyte,thereby preventing the covered portion of the electrode body 100 fromfunctioning as an electrode, in particular in an energy storage unit.The activity of the electrode element 1 is thereby reduced, depending onthe size and configuration of the surface coating D on the electrodebody 100. The surface coating D therefore allows adjustment of thestorage capacity of an energy storage unit that uses the inventiveelectrode element 1.

As an alternative to the version of the electrode element 1 illustratedin FIG. 8, the surface coating D might cover pores or other cavitiesthat run from the surface into the interior of the electrode body 100(such cavities being unfilled, or alternatively having filler materialtherein).

FIG. 9 schematically depicts an version of an energy storage unit 200that has anode 210 and cathode 220, wherein the energy storage unit 200uses the electrode element 1 as an electrode, specifically as anode 210.The energy storage unit 200 is designed as an electrolytic capacitor.The electrode element 1 is made of a valve metal, such as aluminum,tantalum, niobium, or zirconium, with an oxide layer of this valve metalforming the dielectric material of the electrolytic capacitor.

The versions of the invention described above are merely exemplary, andthe invention is not intended to be limited to these versions. Rather,the scope of rights to the invention is limited only by the claims setout below, and the invention encompasses all different versions thatfall literally or equivalently within the scope of these claims.

What is claimed is:
 1. An electrode element (1) for a capacitor (200),the electrode element including an electrode body (100) made of anactive electrode material (E) and a terminal lead electrically connectedto the electrode body (100), wherein the electrode body (100) includesone or more of: a. a cavity (110) upon or within the electrode body(100), wherein the cavity (110) is configured to adapt the electrodeactivity of the electrode body (100) to a predefined electrode activity;b. a partial volume (120) therein, the partial volume (120) containingelectrode material (E) having a lower density than the electrodematerial (E) of the electrode body (100) outside of the partial volume(120), wherein the partial volume (100) is configured to adapt theelectrode activity of the electrode body (100) to a predefined electrodeactivity; c. a surface coating (D) thereon, wherein the surface coating(D) is configured to maintain the surface of the electrode body (100)covered by the surface coating (D) unwetted and functionally deactivatedwhen the surface is in contact with an electrolyte.
 2. The electrodeelement (1) of claim 1 wherein the cavity (110) or the partial volume(120) defines a separation boundary (130), the separation boundary (130)being configured to ease mechanical separation of the electrode body(100) into a first body segment (131) and a second body segment (132) atthe separation boundary (130).
 3. The electrode element (1) of claim 2wherein the cavity (110) or the partial volume (120) extends along: a.an elongated path extending between edges of the electrode body (100),and b. a major portion of the distance between the edges of theelectrode body (100).
 4. The electrode element (1) of claim 1 whereinone or more of: a. several separate cavities (110), and b. severalseparate partial volumes (120), are arrayed in spaced relationship alonga path extending between edges of the electrode body (100), the pathdefining a separation boundary (130) configured to ease mechanicalseparation of the electrode body (100) into a first body segment (131)and a second body segment (132) at the separation boundary (130).
 5. Theelectrode element (1) of claim 1 wherein: a. the electrode body (100)includes two or more partial bodies (400, 401) adjacently arrayed alonga longitudinal axis (L), b. the partial bodies (400, 401) of each pairof adjacent partial bodies (400, 401) are connected by a connectingelement (410) extending therebetween, c. each partial body (400, 401)and connecting element (410) is formed of the active electrode material(E), and d. each connecting element (410) has a smaller cross-sectionalarea perpendicular to the longitudinal axis (L) than its adjacentpartial bodies (400, 401), whereby the cavity (110) is: (1) formedbetween the adjacent partial bodies (400, 401) and adjacent theconnecting element (410), and (2) configured to ease mechanicalseparation of the adjacent partial bodies (400, 401) by severing theconnecting element (410).
 6. The electrode element (1) of claim 1wherein the electrode body (100) includes: a. the cavity (110) upon orwithin the electrode body (100), and b. filler material (F) filling thecavity (110) of the electrode body (100), the filler material (F) havingan electrode activity different from the electrode activity of theactive electrode material (E).
 7. The electrode element (1) of claim 4wherein: a. the cavity (110) is within the electrode body (100), and b.the cavity (110), and the filler material (F) therein, are entirelysurrounded by the active electrode material (E).
 8. The electrodeelement (1) of claim 1 wherein the active electrode material (E)includes one or more of: a. aluminum, b. tantalum, c. niobium, and d.zirconium.
 9. The electrode element (1) of claim 1 defining an electrodeof a capacitor (200).
 10. The electrode element (1) of claim 9 furtherincluding an implantable electrotherapeutic device having the capacitor(200) therein.
 11. The electrode element (1) of claim 1 defining ananode of a capacitor (200).
 12. A method for manufacturing the electrodeelement (1) of claim 1 including the steps of: a. forming the electrodebody (100), the electrode body (100) having a first electrode activity,and b. thereafter: (1) reducing the mass of the active electrodematerial (E) of the electrode body (100), or (2) forming the surfacecoating (D) upon the electrode body (100), whereby the electrodeactivity of the electrode body (100) is adapted to a predefined secondelectrode activity different from the first electrode activity.
 13. Themethod of claim 12 wherein the step of reducing the mass of the activeelectrode material (E) of the electrode body (100) includes forming thecavity (110) upon or within the electrode body (100).
 14. The method ofclaim 12 wherein: a. the step of reducing the mass of the activeelectrode material (E) of the electrode body (100) includes mechanicallyseparating the electrode body (100) into a first body segment (131) anda second body segment (132), b. the separation is along a separationboundary (130) defined on the electrode body (100), the separationboundary (130) extending along an elongated path extending between edgesof the electrode body (100).
 15. The method of claim 14 wherein one ormore of: a. the cavity (110), and b. the partial volume (120), extendsalong: (1) the separation boundary (130), and (2) a major portion of thedistance between the edges of the electrode body (100).
 16. The methodof claim 14 wherein one or more of: a. several separate cavities (110),and b. several separate partial volumes (120), are arrayed in spacedrelationship along the separation boundary (130).
 17. The method ofclaim 12 wherein: a. the electrode body (100) includes a pair of partialbodies (400, 401) adjacently arrayed along a longitudinal axis (L), b.the partial bodies (400, 401) are connected by a connecting element(410) extending therebetween, c. the connecting element (410) has asmaller cross-sectional area perpendicular to the longitudinal axis (L)than the partial bodies (400, 401), whereby the cavity (110) is formedbetween the partial bodies (400, 401) and adjacent the connectingelement (410), a. the step of reducing the mass of the active electrodematerial (E) of the electrode body (100) includes mechanicallyseparating the electrode body (100) into a first body segment (131) anda second body segment (132) by severing the connecting element (410).18. The method of claim 12 wherein the step of reducing the mass of theactive electrode material (E) of the electrode body (100) includesforming the partial volume (120) within the electrode body (100).
 19. Amethod for manufacturing the electrode element (1) of claim 1 includingthe steps of: a. forming the electrode body (100), the electrode body(100) having a first electrode activity, and b. forming one or more of:(1) the cavity (110) upon or within the electrode body (100), (2) thepartial volume (120) within the electrode body (100), and (3) thesurface coating (D) upon the electrode body (100), such formationadapting the electrode activity of the electrode body (100) to apredefined second electrode activity different from the first electrodeactivity.